Programming Forums > Application Development > C++

DaWei · May 30th, 2006, 4:51 PM

Did you get any error messages? If not, open a command window and run your program from there, see what happens. Be clear and thorough in your posts.

Zephirus · May 31st, 2006, 3:37 PM

#include <iostream>

using namespace std;

int main()

{
cout << "HEY, you, I'm alive! Oh, and Hello World!" << endl;
cin.get();

return 0;
}

I changed the \n I know its good C++ practice to use it but I can type endl a lot faster than \n so thats what I walways use. Sometimes you have to put 2 "cin.get();" in there. I know I have to on most of mine to test.

Change the return 1 to return 0 though. With this function, you dont need to return anything at all.

I dont see why this should fail.

OH I just thought of something. in my C++ IDE i have to have to have another include something like staffix.h or something.. Not sure what it is for since im just starting also.

Narue · May 31st, 2006, 4:01 PM

>Try clearing the stream by using 'cin.sync();' before 'cin.get();'.
Um, no. cin.sync() isn't guaranteed to do anything meaningful, much less "clear" the stream. The only portable way to read and discard leftover characters is to read them either with a loop, or with cin.ignore():

(Toggle Plain Text)

// Loop
char ch;
while ( cin.get ( ch ) && ch != '\n' )
  ;

// Ignore
#include <ios>
#include <limits>
cin.ignore ( numeric_limits<streamsize>::max(), '\n' );

g2k556 · May 31st, 2006, 4:26 PM

Okay, I tried what you said DaWai because I didn't get any error messages. I went to the command prompt, said start c:\learingc1.exe. I hit enter, then it went to asking for another command. It must have executed the file, but it appears that there is nothing happening. Is there anyway to cause it to pause.

and narue, i don't quite understand what you mean, you have to remember, I'm only in my first lesson of C++.

DaWei · May 31st, 2006, 4:51 PM

Quote:

Originally Posted by my basic istream sync doc, no guarantees as to validity

Synchronizes the input device associated with the stream with the stream's buffer.
int sync( );

Return Value
If rdbuf is a null pointer, the function returns -1. Otherwise, it calls rdbuf ->pubsync. If that returns -1, the function calls setstate(badbit) and returns -1. Otherwise, the function returns zero.

Note that the extraction function will return if it finds an item eligible to be returned or one that causes an error. "I have to call it twice (or ten times, or whatever)" is not a valid solution to offer. There are reasons for these things. Voodoo is okay, but hard on one's chickens.

If you ran your program, as it is shown, in a commandd prompt window, and saw no output, then you probably have something that is not as shown. As far as endl is concerned, it outputs a newline and flushes the output buffer. There are conditions where the flush is a good idea, but they aren't often seen in these little "Goodbye, cruel world" programs. Still, doesn't mean you haven't something else running that's farbling with things.

JamesCEdmonds · Jun 1st, 2006, 1:07 PM

// My first program in C++.
#include <iostream>
using namespace std;
int main ()
{
cout<<"Any text!";
return 0;
}

I have no problems like this.I also ran it the way you have posted with no problem.Try hitting the compile and run button.

(f9)

Cache · Jun 1st, 2006, 2:10 PM

Quote:

Originally Posted by Narue

>Try clearing the stream by using 'cin.sync();' before 'cin.get();'.
Um, no. cin.sync() isn't guaranteed to do anything meaningful, much less "clear" the stream. The only portable way to read and discard leftover characters is to read them either with a loop, or with cin.ignore():

Quote:

Originally Posted by DaWei

Note that the extraction function will return if it finds an item eligible to be returned or one that causes an error. "I have to call it twice (or ten times, or whatever)" is not a valid solution to offer. There are reasons for these things. Voodoo is okay, but hard on one's chickens.

I see. This harks back to one of my first threads on this forum when I was just starting to learn C++. I was first told to "try flushing it" (the stream). Then told to use cin.sync(), and it "worked". Guess I made the assumption that cin.sync() was clearing the stream and never thought any more of it.

Just for reference:
http://www.programmingforums.org/for...ead.php?t=6640

Won't be making that mistake again.

Narue · Jun 1st, 2006, 3:06 PM

>Then told to use cin.sync(), and it "worked".
This is one of the grey areas. The C++ standard in no way implies that cin.sync() will do what most people expect when they want to "flush" the stream. Unfortunately, many compilers implement it so that it does, and even Stroustrup explicitly (and incorrectly) states that it flushes the stream. The best solution is to avoid it entirely in favor of other solutions that are guaranteed to work as expected.

Ooble · Jun 4th, 2006, 6:16 PM

The C++ FAQ recommends std::cin.clear followed by std::cin.ignore.

May 30th, 2006, 4:51 PM	#11
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Did you get any error messages? If not, open a command window and run your program from there, see what happens. Be clear and thorough in your posts. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

May 31st, 2006, 4:01 PM	#13
Narue Professional Programmer Join Date: Sep 2005 Posts: 419 Rep Power: 4	>Try clearing the stream by using 'cin.sync();' before 'cin.get();'. Um, no. cin.sync() isn't guaranteed to do anything meaningful, much less "clear" the stream. The only portable way to read and discard leftover characters is to read them either with a loop, or with cin.ignore(): (Toggle Plain Text) // Loop char ch; while ( cin.get ( ch ) && ch != '\n' ) ; // Ignore #include <ios> #include <limits> cin.ignore ( numeric_limits<streamsize>::max(), '\n' ); // Loop char ch; while ( cin.get ( ch ) && ch != '\n' ) ; // Ignore #include <ios> #include <limits> cin.ignore ( numeric_limits<streamsize>::max(), '\n' ); __________________ Even if the voices aren't real, they have some pretty good ideas.

Jun 1st, 2006, 1:07 PM	#16
JamesCEdmonds Newbie Join Date: May 2006 Posts: 19 Rep Power: 0	// My first program in C++. #include <iostream> using namespace std; int main () { cout<<"Any text!"; return 0; } I have no problems like this.I also ran it the way you have posted with no problem.Try hitting the compile and run button. (f9) Last edited by JamesCEdmonds; Jun 1st, 2006 at 1:21 PM.

Jun 1st, 2006, 3:06 PM	#18
Narue Professional Programmer Join Date: Sep 2005 Posts: 419 Rep Power: 4	>Then told to use cin.sync(), and it "worked". This is one of the grey areas. The C++ standard in no way implies that cin.sync() will do what most people expect when they want to "flush" the stream. Unfortunately, many compilers implement it so that it does, and even Stroustrup explicitly (and incorrectly) states that it flushes the stream. The best solution is to avoid it entirely in favor of other solutions that are guaranteed to work as expected. __________________ Even if the voices aren't real, they have some pretty good ideas.

Jun 4th, 2006, 6:16 PM	#19
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	The C++ FAQ recommends std::cin.clear followed by std::cin.ignore. __________________ Me :: You :: Them

May 31st, 2006, 3:37 PM	#12
Zephirus Newbie Join Date: May 2006 Posts: 12 Rep Power: 0	#include <iostream> using namespace std; int main() { cout << "HEY, you, I'm alive! Oh, and Hello World!" << endl; cin.get(); return 0; } I changed the \n I know its good C++ practice to use it but I can type endl a lot faster than \n so thats what I walways use. Sometimes you have to put 2 "cin.get();" in there. I know I have to on most of mine to test. Change the return 1 to return 0 though. With this function, you dont need to return anything at all. I dont see why this should fail. OH I just thought of something. in my C++ IDE i have to have to have another include something like staffix.h or something.. Not sure what it is for since im just starting also.

May 31st, 2006, 4:26 PM	#14
g2k556 Newbie Join Date: May 2006 Posts: 7 Rep Power: 0	Okay, I tried what you said DaWai because I didn't get any error messages. I went to the command prompt, said start c:\learingc1.exe. I hit enter, then it went to asking for another command. It must have executed the file, but it appears that there is nothing happening. Is there anyway to cause it to pause. and narue, i don't quite understand what you mean, you have to remember, I'm only in my first lesson of C++.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Programming Forums > Application Development > C++

Need help getting started